If Tuvix is made of a combination of Tuvok and Neelix, does he weigh as much as the two put together? He sure doesn't seem to.

And isn't Janeway's action here murder? She told the Vidiians in "Phage" that her culture doesn't allow her to end one life to save another, what has changed this?

Body Count :

Tuvix is murdered by Janeway.

Plotline

A transporter accident merges Neelix and Tuvok into a single being. After some time the crew discover a method of separating 'Tuvix' - but he's decided that his own life is worth living, and refuses to end it. Janeway decides to kill him anyway.